The present application claims priority of Japanese patent application No. 82/227375, filed Dec. 28, 1982.
This invention relates to silicone amulsion compositions, more particularly to silicone emulsion compositions capable of forming a hardened film having excellent heat and water resistance and high film strength after evaporating water in the composition. The compositions of this invention are therefore suited for use as a treating agent for various types of fibers, asbestos, etc., a releasing agent, a release paper treating agent and so forth.
The silicone emulsion compositions to be applied to such uses must be able to form a hardened film upon evaporation of water in the composition. Many types of such silicone emulsion compositions have been proposed heretofore, among which the following two types are most typical. One is a composition which is produced by adding a catalyst such as an organotin compound to an emulsion of a polydiorganosiloxane containing silanol groups or hydrogen atoms bonded to silicon atoms. This type of composition, however, has the disadvantage that heating at a relatively high temperature is required for forming a hardened film and that the hardened film-forming ability is lost a short time after addition of the catalyst. Another type of composition is a polyorganosiloxane latex obtainable by emulsion polymerization of an organoalkoxysilane having amino, epoxy or mercapto groups and a cyclic organsiloxane (Japanese Patent Laid-Open No. 131661/1979). This latex is advantageous in that all the components can be stored in one package, and that heating to a relatively high temperature is not required for forming a hardened film. However, it has a drawback in that the film formed therefrom is subject to certain limitations on its mechanical strength and adhesiveness and is therefore unsuited for use as a coating agent.
In view of these problems on the prior art, the present applicant has pursued further research for a silicone emulsion composition which retains its original properties even if kept in storage for a long time and which is capable of forming a hardened film with high strength and good adhesiveness after evaporation of water contained therein with no need for using a catalyst and, as a result, has succeeded in obtaining a silicone emulsion composition which is free of the prior art problems by blending an alumina sol in an emulsion of a polyorganosiloxane containing silanol groups. The present invention has been completed on the basis of this fact.